Noise fears over South Mountain Freeway confirmed

Corinne Purtill
The Arizona Republic
Jan. 6, 2006 11:45 AM 

Engineers at the South Mountain Citizens Advisory Team meeting on Thursday night confirmed something opponents of the proposed South Mountain Freeway have feared: The highway, if built, is going to make some noise.

Once the 22- to 26-mile proposed freeway is open to traffic, homes within 1,400 feet - just more than a quarter-mile - of the freeway will hear noise "above acceptable levels," according to a report released at Thursday's meeting.

The acceptable level is about 67 decibels, or the point at which two people standing next to each other having a conversation have to raise their voices to be heard, said Fred Garcia, an environmental planner with the Arizona Department of Transportation.

ADOT will build walls to muffle the noise in neighborhoods, engineers said. Those barriers are most helpful for people living within 300 to 500 feet of them, Garcia said. Homes beyond that boundary will actually hear the freeway more than those closest to it.

The freeway would connect Interstate 10 in the West Valley to I-10 in the Southeast Valley, bypassing Phoenix. ADOT wants to pick a West Valley route by the end of this year, finalize the entire alignment by late 2007 and start construction in 2009.

It's too early in the design process to know where and how tall the sound walls would be. Typical noise walls throughout the Valley are 10 to 20 feet high, with an average height of 14 to 16 feet.

Freeway noise is caused by three things: car engines, exhaust, and most of all the sound of tires on the pavement. To mitigate the last item, the freeway will be paved with rubberized asphalt, a tool that reduces freeway noise up to 75 percent, said ADOT engineer Dan Lance.

Peggy Eastburn, a member of the advisory team, said that her Estrella home is one-eighth of a mile from I-10. Before it was paved with rubberized asphalt, her family couldn't hear a television with the doors open.

"With rubberized asphalt, you don't hear it anymore," she said.

Engineers at the meeting also discussed possible hazardous material sites that could be disrupted by freeway construction. The potential West Valley alignments - which would link the freeway to I-10 at 55th Avenue, 71st Avenue or Loop 101 - would bypass sites where contaminated materials lurking underground could be brought to the surface during construction. Those sites will require special handling, said Kelly Kading, an engineer with HDR, a consulting firm assisting ADOT.